I'm currently in the process of working on a short sci-fi thing, and I just found what I think is a jackpot of Alliance armor from a rental house. The same rental house that has the original space walk suits from Firefly for rent as well.

They also have the following, which all look suspiciously similar to Alliance armor.

The "Space Walk" suits are from the Kurt Russell flick "Soldier," and the original purplebellies armor from The Train Job was partially repainted stuff from Starship Troopers, which is what your third set appears to be (though modified again).

I don't recognize those metal helmets, and their associated armour, but I suspect they're from some late 90's / early 2000's sci-fi movie as well. Might even be the bad guy costumes from Soldier; it's been a while since I saw it.